GEOmap (version 2.5-11)

CCcheck: Counter Clockwise check

Description

Check for counter-clockwise orientation for polygons. Positive is counterclockwise.

Usage

CCcheck(Z)

Value

j

sign of area

Arguments

Z

list(x,y)

Author

Jonathan M. Lees<[e-mail]>

Details

Uses sign of the area of the polygon to determine polarity.

Examples

Y=list()
Y$x=c(170,175,184,191,194,190,177,166,162,164)
Y$y=c(-54,-60,-60,-50,-26,8,34,37,10,-15)

plot(c(160, 200),c(-85, 85), type='n')
points(Y)
lines(Y)

CCcheck(Y)


Z = list(x=rev(Y$x), y=rev(Y$y))

CCcheck(Z)